Stress-strain State Research Articles

Dualistic effect of the deformation of protective structures made of broken rock in mine workings under static load

Purpose is to reveal physical essence of the dualistic (double) nature of deformation effects and their influence on the mechanical properties of protective structures made of broken rock while unloading coal-bearing mass to ensure stability of side rocks and operational conditions of the development mine working within the working areas of coal mines. Methods. The deformation properties of protective structures made of broken rock was modeled on experimental samples during their static load in terms of uniaxial compression with the possibility of lateral expansion of the original material or its compressive stress. Findings. A dualistic effect of deformations for the conditions of uniaxial compression of protective structures was revealed. Under the effect, a complex transformation of volume and shape occurs in the structures caused by the process of relative changes in the backfill material volume. The observed phenomenon occurs within the range of 0.12 ≤δV ≤ 0.32 and the values of the compaction coefficient of broken rock being 1.13≤k con. ≤ 1.47, depending on the granulometric composition of the source material and its bulk density. It was established that under conditions when broken rock is compressed, there is an effect of forming the bearing capacity of protective structures, which is observed when a relative change in the volume of backfill material is 0.14 ≤ δV ≤ 0.38, and its compaction factor reaches 1.16 ≤ kcon. ≤ 1.59. Depending on the homogeneity degree of the backfill material of protective structures, when comparing the values of kcon., a dualistic (double) effect is manifested in the difference of deformation characteristics of broken rock under uniaxial and compressive stress, reaching two or more times. Originality. A regularity was established that determines the relationship between compaction factor kcon. of broken rock and a relative change in the volume (δV) of backfill material, which makes it possible to evaluate bearing capacity of protective structures, being under static load in a stress-strain state. Practical implications. The research results can be used to substantiate the selection of a method to protect development mine working with flexible supports made of broken rock. To clarify the assessment of bearing capacity of such structures, it is advisable to carry out specific field studies in mine conditions.

Numerical modelling of the pit wall stability while optimizing its boundaries to ensure the ore mining completeness

Purpose is to assess changes in the stress-strain state of walls along the whole periphery of a super-deep open pit while optimizing its current and final boundaries for the complete ore excavation. Methods. Finite element 3D analysis of stress-strain state (SSS) of the soil and rock mass relies upon the models varying in their scales. Macrolevel model includes the full pit helping perform initial evaluation of its stability depending upon changes in the general wall slope along the pit periphery. Then, the macromodel is separated into sectoral models with smaller scales oriented radially in such a way to include potentially unstable wall areas. The sectoral models make it possible to show the complex bench line in more detail after the peripheries were optimized in terms of economic factor and simulate layered structure of the rock mass. Elastoplastic model of the medium as well as Mohr-Coulomb strength criterion has been implemented using RS3 (Rocscience) program codes. Findings. An indicator of wall strength (safety factor) distribution along the pit periphery has been identified; potential sliding surfaces within each of the separated open pit sectors have been localized based upon the shear strength reduction (SSR) procedure. Influence by the general wall slope as well as by the indicator of the ore excavation completeness on the stripping ratio has been demonstrated. Originality. For the first time, two-level modelling has shown difference in a safety factor depending upon a model scale and a reflection degree of the soil-rock mass structure. In the context of the actual mining and geological conditions of Kacharsky open pit, changes in the safety factor along the pit periphery have been identified depending on the general slope of the wall. Practical implications. Based upon the pit wall stability along the whole periphery, the possibility has been substantiated to optimize its design boundaries for the excavation of those amenable ore reserves, occurred near them, inclusive of ore, occurring in a bottom, which mining is impossible due to inaccessibility.

Determination of the Thermal and Stress-Strain State of the Medium-Pressure Rotor of the T-100/120-130 Turbine after Damage to the Blades

Determination of the Thermal and Stress-Strain State of the Medium-Pressure Rotor of the T-100/120-130 Turbine after Damage to the Blades

Study of the stress-strain state of the pontoon element of the support block

Study of the stress-strain state of the pontoon element of the support block

Research into mechanical properties of ore and rocks in the ore deposits with assessment of the mass stress state natural field

Purpose. The research aims to conduct a comprehensive study of the mechanical properties of ores and rocks within the Zhilandy Group field, as well as to assess the natural field of mass stress state to solve geomechanical problems in optimizing mining operations. Methods. To determine the boundary conditions when measuring the stress-strain state of the mass, a complex methodology is proposed, including stress measurements using hydraulic fracturing methods of the wells and determining the physical-mechanical properties of rocks. Five rock probes have been tested. Twelve tests (six tests in natural and six in water-saturated states) have been conducted for each probe. Findings. Hydraulic fracturing tests at the metering stations show significant tectonic stress due to the shape of structural folds and the mass fracturing. It has been revealed that the hard rock mass is characterized by non-uniform fracturing. It is of tectonic origin and averages between 10-15 and 15-25 fractures per meter for different lithological varieties. The maximum horizontal stress at the stations is oriented along an azimuth of 70° ± 10. Originality. The influence of water saturation on the reduction of strength and deformation characteristics of rocks has been determined for the conditions of the Zhilandy Group field, which shows significant variations depending on the rock type. Especially important is the revealed fact of a significant decrease in uniaxial compression and uniaxial tensile strength, as well as a decrease in Young’s modulus and cohesion factor. Linear dependences of stresses occurring with depth have been obtained from the measurement results. Practical implications. The results obtained are of significant importance for the mining industry. Understanding the extent of reduction in strength characteristics during water saturation and assessing the natural field of the stress mass state allows more accurate prediction of rock behavior.

Determining the parameters for the overlying stratum caving zones during re-peated mining of pillars

Purpose. The research aims to determine the parameters for the overlying stratum caving zones above the mined-out space during repeated mining of pillars at the Zhomart Mine of the Zhaman-Aybat field for the purpose of predicting hazardous zones of influence of mining operations. Methods. Research includes an analysis of the results of previous in-situ studies conducted using seismic surveys, as well as modeling with the Examine2D software to determine the stress-strain state of the overlying stratum mass. The elastic and strength characteristics of an anisotropic mass are used for modeling, taking into account the generalized Hoek-Brown criterion with the Geological Strength Index (GSI) based on a geomechanical description of the mass quality. Comparative analysis of modeling results with seismic survey results is conducted to confirm the effectiveness of the developed methodology. Findings. The research provides an opportunity to determine the overlying stratum caving parameters, such as the caving arch height and the condition for complete undermining of the overlying stratum at the Zhaman-Aybat field at different spans of the mined-out space (from 50 to 350 with a step of 50 m, reaching the maximum span of 370 m). Originality. . It has been determined that the caving arch height depends on the outcrop span and increases exponentially (hcav = 16.473 e0.008Le). In addition, the condition of the earth’s surface complete undermining has been identified depending on the depth of the site to be gotten. Practical implications.The research results can be used to develop a normative document for calculating the earth’s surface shear during the repeated mining of pillars at the Zhomart Mine of the Zhaman-Aybat field. The data obtained will also be useful in planning repeated mining and predicting the earth’s surface shear to avoid negative impacts of mining operations on surface structures.

Study of the causes of the collapse of a high-rise chimney under conditions of long-term operation

This article analyzes the causes of the collapse of a high-rise chimney in Petropavlovsk. A study of the factors of long-term (over 60 years) operation of a high-altitude (H=150 m) chimney was carried out. The analysis of the constructive solution of the pipe was carried out, and the study of the operating conditions was performed. To theoretically assess the technical condition and stress-strain state factors (SSS) of the collapsed chimney, automated verification calculations were carried out based on the actual parameters and characteristics obtained during the last technical inspection. An automated verification calculation of SSS factors determining the bearing capacity of an object (its strength, rigidity, reliability, and durability) has been performed. Theoretically, the physical wear of the object has also been carried out. Based on the study of the available technical documentation and conducting a continuous, detailed instrumental examination of the facility, the expert organization established the significant causes that led to the pipe accident.

Electrical conductivity model for transversely isotropic rocks with interconnected cracks

The electrical conductivity of subsurface rocks is generally anisotropic. The anisotropy of the subsurface electrical conductivity provides important information on the stress-strain state and geodynamics. To quantitatively interpret anisotropic conductivity structures revealed by electromagnetic surveys, it is essential to use a mixing model considering the anisotropy. Although there exists a mixing model for transversely isotropic rocks with crack-shaped pores, the previous model seems inappropriate in interpreting conductive anomalies revealed by electromagnetic exploration because cracks are assumed to be isolated in the model. Therefore, this study develops a theoretical mixing model for transversely isotropic rocks with mutually interconnected cracks by a statistical approach. The derived mixing model considers the macroscopic tortuosity of a collection of cracks as well as the tortuosity of each crack. The derived model can represent general transverse isotropy and includes the isotropic and parallel models as special cases. I compare the developed model to previously proposed mixing models, showing that the developed model can reproduce a much wider range of anisotropy than the already-existing anisotropic mixing model. By applying the developed model to an example of the anisotropic conductivity in the oceanic upper crust inferred by electromagnetic exploration, I demonstrate that the developed mixing model enables us to quantitatively infer the crack orientation and fluid volume fraction that reproduce significant anisotropic conductivity found by field observations. Furthermore, I compare the developed model to the anisotropic seismic velocity model for fluid-filled cracks.

Modeling of ice-matrix composite fracture

This article discusses the results of a study that used the structural approach to conduct multiscale modeling of composite materials. These materials are composed of an ice matrix that has been enhanced with high-strength basalt fibers. The research involved numerical modeling to analyze the fracture process of composite materials made by freezing fresh water with added basalt fibers. The analysis included experimental data from samples of pure ice and composites with different amounts of filler. The effective modulus of elasticity of the composites was determined by considering the quantity of basalt fiber reinforcement. The discrepancy between the strength obtained by finite element complex ANSYS numerical calculation and the experimental data was revealed by a series of macroscopic test calculations of the composite material sample, according to which the effective modulus of elasticity of the composite was recalculated and corrections were introduced into the Voight and Reuss models, taking into account the non-uniform distribution of the fibers and the non-ideal adhesion between the fibers and water ice. A stochastic model of crack growth at the micro level was also used with the data on the diameter and length of basalt fibers and their random distribution in the layers of the composite material. Using the newly acquired effective elastic moduli and the SmartCrackGrowth algorithm, a satisfactory agreement of the crack growth rate with the obtained by stochastic calculation was achieved. The refined method of effective elastic moduli and multilevel model of stress-strain state calculation of composite materials are recommended for assessing the strength of ice cover and designing winter roads with high load-bearing capacity and long operational duration in the Arctic and Subarctic environments.

On a Method for Calculating Bending and Shear Vibrations of a Porous Piezoelement in the Low-Frequency Region

Introduction. Devices for collecting and storing energy from the external environment are low-power sources of electric energy that are actively used. The autonomous devices for monitoring the damaged condition of various structures include them as well. The working element of these devices is a piezoelectric generator (PEG) — a converter of mechanical energy into electrical energy. The design of PEG is associated with the preliminary construction of their mathematical and computer models, with the help of which the calculation and optimization of structures is carried out. One of the ways to model and calculate PEG is to develop approximate calculation methods based on applied theories. The applied theories for calculating bending vibrations of multilayer piezoactive plates are known and previously developed in the literature. However, in the scientific literature there is not enough information about bending and shear vibrations as a tool for improving the efficiency of engineering calculations of the described structures. The objective of this work was to develop an applied method for calculating bending and shear vibrations of piezoceramic plates, including porous ones.Materials and Methods. Piezoceramics PZT-4, including porous ones, were used as the piezoactive material of the plate. When using porous ceramics, the rigidity of the structure decreased to a greater extent than the piezoelectric modules, which made it possible to obtain a more effective PEG under mechanical action. The mathematical formulation was carried out within the framework of the linear theory of electroelasticity with plate polarization in thickness. The sides of the plate were electrodated, the right side was fixed, and a smooth contact in the vertical wall was set on the left side. Steady-state vibrations of the plate were caused by pressure on the front surfaces of the plate or the difference in electrical potentials at the electrodes. To calculate the characteristics of PEG, the authors proposed an applied theory based on hypotheses about the distribution of characteristics of the stress-strain state and the electric field.Results. Transverse vibrations of a piezoceramic plate in the low-frequency region (below the first bending-shear resonance) were studied. Due to the fact that the mathematical formulation was considered within the framework of the linear theory of elasticity, the problem was divided into the sum of two. The first one took into account the mechanical effect: a distributed load and a transverse force at the left end acted on the front surfaces of the plate, and the potentials at the electrodes were zero. In the second task, there were no mechanical loads, but the potential difference was set at the electrodes. Based on hypotheses about the distribution of deformations, mechanical stresses and electric potential, both problems were reduced to a system of ordinary differential equations and boundary conditions. Comparison with the results of calculations by the finite element method in the ACELAN package showed the adequacy of the proposed applied theory in the low-frequency region.Discussion and Conclusion. Since the formulation of the problem was considered in the linear theory of electroelasticity, and the low-frequency region was studied, the work succeeded in dividing the problem of bending-shear vibrations of a porous piezoceramic plate into two: bending — with mechanical action at zero potentials, and shear — when setting the potential difference and zero mechanical action. The corresponding hypotheses about bending and shear were used. Two systems of ordinary differential equations and boundary conditions, which were solved analytically without the use of “heavy” finite element packages, were constructed. To compare the results and confirm the adequacy of the proposed method, the finite element modeling of such tasks was carried out in a specialized ACELAN package. The comparison showed that the error in determining displacements and electric potential when using this approach, in the case of setting mechanical loads and potential differences, did not exceed 6%. The method developed in the paper can be applied in the design of piezoelectric generators for energy storage in the low-frequency region.

Influence of soil base deformation methods on the formation of the stress-strain state of retaining walls

The results of numerical modeling of the interaction between a pile retaining wall and the soil base using the software complexes "Plaxis" and "LIRA-SAPR" are presented. A comparison of the stress-strain state of retaining walls using different calculation methods, taking into account the presence of rock soil, has been performed. In the first variant, the active pressure on the wall was determined manually in accordance with the current standards [3], and the subsequent calculation was carried out in the "LIRA-SAPR" software complex. The "pile-soil" system was modeled using FE 57, which are interconnected by FE 10 (rod), and the values of horizontal stiffness (Rx,y) were determined according to the requirements of [3]. In the second variant, the retaining wall calculation was performed in "Plaxis 2D". The soil behavior model is "Mohr-Coulomb", and for rock - "Hoek-Brown". It was considered that rock soils lie at the base of the retaining wall, which revealed significant differences in the distribution of bending moments along the length of the retaining wall. It was established that the stress-strain state in the first variant significantly differs from the second. The difference in maximum horizontal displacements after the calculation by the first and second methods was shown. Differences and variations in the values of bending moments occurring in the retaining wall were investigated. The importance of using modern geotechnical calculation software complexes for a more detailed and accurate analysis of structures and foundations was demonstrated. Additionally, an assessment of the impact of variations in the parameters of the soil and retaining wall models on the calculation results was conducted. The research results allow recommending the use of a comprehensive modeling approach to enhance the reliability and efficiency of retaining wall design. The analysis also shows that the application of different soil behavior models can significantly affect the final calculation results, highlighting the need for careful selection of modeling parameters. The obtained results have significant practical value for engineers and designers, as they allow for more accurate prediction of the behavior of retaining walls under various operating conditions. This contributes to improving the safety and cost-effectiveness of construction projects.

The use of planar and three-dimensional calculation models for the numerical modeling of retaining walls in conditions of dense urban construction

In modern realities, the construction of multi-story buildings increasingly has to be carried out in the conditions of dense urban development. Since high-rise buildings are characterized by the presence of deep pits, there is a need to select the parameters of the enclosing structures (retaining walls) and take into account the influence of the pit arrangement and enclosing structures on the existing building. Numerical simulation of the stress-strain state (SSS) of the elements "soil base - existing structures - pit enclosure" was performed to assess the impact of choosing the dimensions of the calculation scheme when designing a deep pit and assessing its impact on existing buildings and selecting effective parameters of enclosing structures. with different dimension options (flat two-dimensional and spatial three-dimensional) calculation scheme. Modeling was performed using the finite element method using a nonlinear model of soil deformation in the Plaxis software package. Since the soil conditions within the construction site are complex (the presence of a significant layer of plastic and flowing clay soils and powerful aquifers), the level of groundwater within the construction site was taken into account in the modeling and the effect of water lowering during the development of the pit was modeled accordingly for a more correct assessment of the stress-strained state of pit enclosure elements and the impact on existing structures. Numerical calculations of retaining walls provide for taking into account the technological sequence of the construction of retaining walls and modeling of the step-by-step development of the pit. Studies have shown that the use of a spatial finite-element model of the system "soil base - existing structures - pit enclosure" provides an opportunity to more correctly and effectively assess the stress-deformed state of system elements due to taking into account the spatial rigidity of the elements of the pit enclosure and the foundations of existing structures. The values of the displacements of the retaining walls obtained by the calculation of the spatial finite element model (FEM) are 20% smaller than the values obtained using the plane FEM. The values of the bending moments obtained by the calculation of the spatial FEM are 10% smaller than the values obtained using the plane FEM.

Численное моделирование процесса прерывистого резания с использованием ПО LS-Dyna

The results of numerical simulation of the stress-strain and thermal state in the cutting zone during face milling are presented. The simulation process was performed using LS-Dyna dynamic process research software

Revealing the influence of wind vortex shedding on the stressed-strained state of steel tower structures with solid cross-section

This work investigated the effect of vortex shedding during the action of wind on tower structures with a solid cross-section. Failure to take into account this influence, together with the manifestation of the phenomena of physical wear of structures during long-term operation, can lead to building accidents. The object of the research are tower structures with a solid cross-section, which are widely used in modern infrastructure ‒ advertising pylons with a transparent advertising structure with a height of about 12, 22, 25 m, and a flagpole with a height of 48 m. The most frequent manifestations of oscillations according to the first natural frequency and shape have been considered, which occur even with moderate winds and when a large number of oscillation cycles occur. In this work, the number of oscillating cycles per year was determined and estimated based on the archive of meteorological observations. It was found that the number of oscillating cycles due to the action of wind excitation for the example of the structures under study is from 2.6 to 14.4 million per year, which requires the mandatory limitation of stresses in the parts of structures during the design to enable their durability. The magnitude of forces from vortex shedding for the studied structures ranges from 2.9 to 43.5 % of the forces caused by the influence of the frontal wind, depending on the height of the structure. Thus, it was found that the influence of vortex shedding is very insignificant for structures up to 12–15 m high and increases for structures 20 m and higher. Rational forms of the cross-sections of structures were established to reduce the influence of vortex shedding ‒ these are cross-sections of a circular and a cross-section close to it. In a general formulation, these are sections for which peak stresses relative to forces in one plane fall into the neutral zone for stresses from forces in another plane. Recommendations have been also given on the simultaneous consideration of forces from the action of frontal wind on the structure and vortex shedding since both manifestations of wind action on tower structures cannot be separated

НЕЛИНЕЙНАЯ ДЕФОРМАЦИОННАЯ МОДЕЛЬ СП 63.13330 В СТАДИЙНОЙ ПОСТАНОВКЕ

Normative documents in the field of reinforcement of reinforced concrete structures and the design of prefabricated monolithic structures fairly prescribe consideration of the initial stressstrain state of structures before reinforcement. The calculation can be performed using a normalized nonlinear deformed model according to SP 63.13330. At the same time, it does not explicitly provide for a calculation in several stages. The aim of the study is to develop a calculation method based on a normalized nonlinear deformation model in a staged formulation with minimal differences from the provisions of SP 63.13330. To achieve the goal, the following tasks are set: development of a calculation method, implementation of the method in the form of a universal program and verification of the developed program. The article presents a universal nonlinear deformation model in a staged formulation, which allows, within the framework of certain ratios, to calculate the strength and crack resistance of structural sections at an unlimited number of work stages, taking into account reinforcement, prestressing, initial stresses and cyclic loading (unloading and reloading). The method is implemented as a program in the Python programming language and verified on full-scale and numerical (finite element method) experiments. If we assume the initial stresses and deformations to be zero and calculate in one stage, then the proposed model is reduced to the SP 63.13330 model. For this reason, changing the norms according to the proposed method will not affect the current algorithms for calculating structures in one stage, however, it will significantly increase the scope of the model for calculating prefabricated monolithic, steel-reinforced concrete and reinforced structures. In addition, the accuracy of calculations of prestressed structures will increase, and it will be possible to calculate the cyclic loading of the section.

Study of the stress-strain state of the loess soil base of an eccentrically loaded tower foundations, with taking into account the possible water saturation of the soil

This article provides the design of the tower shallow foundations using numerical simulation in the "Midas GTS NX" software. The foundations are four separate structures that perceive the bearing reactions from the tower supports. Depending on the wind load direction, the support reactions change both quantitatively and qualitatively. So, one foundation can accept a compressive force, the other one can accept a pull-out force. In this study, two variants of wind loading are considered: the wind load acts on the tower face or on the tower edge. The geological conditions of the research site are taken as simplified. The soil base consists of one engineering-geological element, which is a loess soil. Numerical simulation of the soil massif was implemented by using volumetric finite elements. An elastic-plastic deformation law and a Mohr–Coulomb failure criterion were applied for these finite elements. The design provided for the calculation of the tower foundation on a natural basis and with the arrangement of a compacted sub-base. Research was carried out for the foundations of the tower construction in four stages: 1) soil base in its natural state; 2) arranged compacted sub-base; 3) natural basis with local water saturation of the soil; 4) compacted sub-base with local water saturation of the soil massif. Simulation of the arrangement of the compacted sub-base occurs by replacing the stiffness of the finite element at a certain stage of the calculation. The soil water saturation simulation algorithm is performed in a similar way - there is a change in the physical and mechanical characteristics of certain finite elements. The localization of saturation zones was chosen from the conditions of the most unfavorable combinations of loads and vertical movements of the foundations. An analysis of the stress-strain state of the soil base of foundations under the tower on a natural base and with the arrangement of a compacted sub-base was performed. The scheme of the applied load on the foundation and the possible local water saturation of the loess soil at the base of the foundations were taken into account

Numerical studies of the distribution capability of a continuous linear strain soil base model for largesized raft foundations

The paper examines the existing methodology for determining the main design parameters of the model in the form of a continuous linearly strained layer of finite distribution capability (the design thickness of the layer H0 and design stress-strain modulus E0) to simulate the adequate interaction between soil bases and large-size slab foundations. The aim of this work is to numerically study the stress-strain state of a uniformly loaded flexible rectangular foundation slab when the thickness of the soil base model layer is reduced in the form of a continuous linearly deformed layer of finite distribution capacity. Numerical studies of the effect of the thickness of the layer of the specified soil base model that interacts with a large-size flexible slab foundation of various rectangular shapes in plan were conducted in the SCAD package using the finite element method. The numerical study results have shown that when the ratio H0/Ha (the design thickness of the layer of the soil base model H0 to the actual compressible thickness of the soil base Ha) decreases, the maximum moment forces along the orthogonal axes of rectangular foundations decrease to 50% because of the decrease in the distribution capability of the soil base model and, accordingly, in the edge reactions R under the slab at equal average settlements of the slab saver. Numerical studies have shown interesting results on the distribution of moment forces in flexible rectangular slabs, where the maximum is outside the center of gravity of a uniformly loaded raft, which confirms the peculiarity of the interaction of flexible slabs with relatively narrow compressible layers under the sole. With an appropriate in-situ experimental justification, the use of the soil base model in the form as a continuous linearly strained layer of finite distribution capability with the design parameters (H0 and E0) rather than with the actual parameters (Ha and Ea) in calculations of large-size slab foundations can be of fundamental practical importance in their rational design, as the reinforcement can be reduced to 50%

FORECASTING THE FINAL RESOURCE OF THE REINFORCED CONCRETE CHIMNEY PIPE OF THE COKE CHEMICAL PRODUCTION

A comprehensive study of the technical condition, corrosion processes, damage and load-bearing capacity of the reinforced concrete chimney pipe, which removes the gas-smoke mixture formed in the technological processes of coke-chemical production and is an aggressive environment, was performed. A methodology for predicting the remaining resource of the pipe structure has been developed. It was established that the damage that determines the ultimate resource is the collapse of the lining, after which active corrosion damage of the reinforced concrete structure occurs. An analysis of the composition and temperature-moisture regime of the aggressive medium was performed. It was established that it is gaseous, the most aggressive components of which are acid gases, the degree of aggressive action is moderately aggressive, possibly strongly aggressive. Corrosion of concrete progresses in a concentric front from the inner surface of the chimney to the outer surface at a rate of 1.2 to 4.8 mm/year. The corroded layer of concrete loses its strength and protective properties to the reinforcement. An analysis of the stress-strain state of the pipe taking into account corrosion damage was performed, the most heavily loaded dangerous zone and its structure were determined, and the limit values of the wall thickness and the depth of corrosion damage in this zone were determined, which ensure the fulfillment of the conditions for bearing capacity. Based on the values of the corrosion rate, the time to reach the limit state is determined. It is shown that without repair and protection measures, the remaining service life of the pipe does not exceed 11 years. It is recommended to carry out a major repair of the pipe as soon as possible with the elimination of damage and restoration of the lining, or no later than after 10 years to carry out the liquidation of the structure with the construction of a new one.

To the study of the stress-strain state of an elastic foundation in the presence of vertical and horizontal injectors

To the study of the stress-strain state of an elastic foundation in the presence of vertical and horizontal injectors

A soil base model of adjacent various story structures

In modern geotechnical engineering, owing to the development of information technology and availability of powerful packages for the calculation of the entire base - foundation - structure system, one of the main research areas is to develop, improve and investigate soil base models to ensure the adequate interaction between the components of the system during the construction and operation of buildings and structures (hereinafter referred to as the “structures”). The paper proposes an improved soil base model in the form of a continuous layer of finite distribution capability to simulate and calculate adjacent multistory structures in the base - foundations - structures system using powerful calculation packages such as SOFiSTiK, ABAQUS, PLAXIS, SCAD, Lira and others. The improved model considers the parameters of the stress-strain properties of the soils of the bases, the geometric profile taking account of the distribution capability of the base and different boundary conditions, but differs from the existing models in that it has a stepped geometric profile at the lower boundary of the model because of different compressible layer depths under each foundation of the structures. The use of this model improves the accuracy of simulating a soil base for large-sized foundations of adjacent structures to obtain reliable results of the stress-strain state of the base - foundations - structures system. An example demonstrates how to simulate and calculate raft foundations of a two-section multistory building in the base - foundations - structures system that interacts with an improved soil base model (linear strains of soils under loads are considered here) with reference to different numbers of stories of the sections. The numerical study results show on a specific calculation example that considering different compressible layers depths in the model under differently loaded foundations results in an increase in moment forces of up to 65% as compared with simulating the whole compressible layer, which may lead to the disruption of large-sized raft foundations.